An ultrasonic diagnostic apparatus for imaging ultrasonic images for diagnosis of an object to be examined is for transmitting/receiving ultrasonic waves between the object via an ultrasonic probe, and for reconstructing ultrasonic images based on the receiving signals outputted from the ultrasonic probe.
As for such ultrasonic diagnostic apparatus, a so-called harmonic imaging method is known for imaging contrast effect of ultrasonic contrast medium (hereinafter referred to as contrast medium). For example, contrast medium is injected into an object and dispersed in the diagnostic region. When ultrasonic waves are irradiated to the dispersed contrast medium, harmonic components originating from nonlinearity of the medium contrast are generated. By detecting and imaging the generated harmonic components, diagnosis of blood vessel shape or discrimination of tissues is performed (for example, refer to Patent Document 1).
Patent Document 1: JP-A-H11-76231
Meanwhile, when ultrasonic waves are irradiated to the object to which contrast medium is injected, harmonic components not only originating from contrast medium but also originating from biological tissues of a part such as an organ are dispersed. When those harmonic components are detected and imaged, harmonic components originating from biological tissues are displayed being superimposed on the harmonic components originating from contrast medium as blind noise. Therefore, there are occasions that the contrast condition of the contrast medium cannot be grasped due to difficulty in, for example, accurate visual recognition of signals originating from the contrast medium on an ultrasonic image. The method in Patent Document 1 does not address such a problem. Moreover, since a local filter is used for eliminating second harmonic components, necessary contrast echo signals are also eliminated, whereby lowering signal intensity of the contrast echo signals and deteriorating image quality.
Given this factor, there is a need for creating sharper images of the signals originating from contrast medium and the signals originating from biological tissues. The objective of the present invention is to provide an ultrasonic diagnostic apparatus and ultrasonic image display method capable of creating shaper images from the signals originating from contrast medium and the signals originating from biological tissues.